JP2010263627A - Transmission circuit, differential signal transmission circuit, and test apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To switch a transmission line for transmitting a component containing a direct current component and a transmission line for transmitting a high-frequency component. <P>SOLUTION: There are provided a transmission circuit, a differential signal transmission circuit and a test apparatus. The transmission circuit transmits signals between an input terminal and an output terminal and includes: a first high-frequency signal passing section that blocks a low frequency signal that has a frequency lower than a predetermined reference frequency in a signal received from the input terminal, and transmits a high-frequency signal that has a frequency higher than or equal to the predetermined reference frequency to the output terminal; an input-side low frequency signal passing section that passes the low-frequency signal in the signal from the input terminal and make the high-frequency signal attenuate; an output-side low frequency signal passing section that transmits to the output terminal the low-frequency signal passed through the input-side low frequency signal passing section and attenuates the high frequency signal from the first high frequency signal passing section; and a switching section that switches a connection between the input-side low-frequency signal passing section and the output-side low-frequency signal passing section. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a transmission circuit, a differential signal transmission circuit, and a test apparatus.

In some cases, a transmission circuit is used that can switch between DC coupling that includes a direct current component of a signal to be transmitted and AC coupling that transmits an alternating current component excluding the direct current component and the low frequency component. For example, a transmission circuit that switches between a transmission line that transmits a component including a DC component and a transmission line that transmits a high-frequency component using a switch has been used (see, for example, Patent Document 1).
Japanese Patent Application Laid-Open No. 6-207953

  In a transmission circuit that switches between a transmission path that transmits a component including a direct current component and a transmission path that transmits a high-frequency component, the transmission band of the changeover switch can be made equal to the signal band for transmission, or the reflection of the changeover switch can be reflected. It was designed in consideration of the influence. In addition, in the transmission path for transmitting the high frequency component, the changeover switch or the wiring branched to the transmission path for the low frequency component becomes a stub, and reflection or the like occurs to adversely affect the high frequency transmission.

  In order to solve the above-mentioned problem, in the first aspect of the present invention, a transmission circuit for transmitting a signal between an input terminal and an output terminal, wherein the signal is less than a predetermined reference frequency in the signal from the input terminal. The high frequency signal may be attenuated by blocking the low frequency signal and passing the low frequency signal in the signal from the input terminal through the first high frequency signal passing unit that transmits the high frequency signal higher than the reference frequency to the output terminal. , An input-side low-frequency signal passing unit that insulates a high-frequency signal from the input terminal, and a low-frequency signal that has passed through the input-side low-frequency signal passing unit is transmitted to the output terminal, and the first high-frequency signal passing unit The high-frequency signal from the output terminal may be attenuated, and the connection between the output-side low-frequency signal passing part that insulates the high-frequency signal from the output terminal, the input-side low-frequency signal passing part, and the output-side low-frequency signal passing part or not To provide a transmission circuit comprising a switch unit, the switching.

  It should be noted that the above summary of the invention does not enumerate all the necessary features of the present invention. In addition, a sub-combination of these feature groups can also be an invention.

1 shows a configuration of a transmission circuit 100 according to the present embodiment. A configuration of a differential signal transmission circuit 200 according to the present embodiment is shown together with a differential signal source 210. An example of the signal transmission result by the differential signal transmission circuit 200 according to the present embodiment is shown. An example of the signal transmission result by the differential signal transmission circuit 200 according to the present embodiment is shown. The 1st modification of the differential signal transmission circuit 200 which concerns on this embodiment is shown. The 2nd modification of the differential signal transmission circuit 200 concerning this embodiment is shown. The 3rd modification of the differential signal transmission circuit 200 which concerns on this embodiment is shown. The 4th modification of the differential signal transmission circuit 200 concerning this embodiment is shown. 5 shows a fifth modification of the differential signal transmission circuit 200 according to the present embodiment. A configuration example of a test apparatus 1000 according to the present embodiment is shown together with a device under test 10.

  Hereinafter, the present invention will be described through embodiments of the invention, but the following embodiments do not limit the invention according to the claims. In addition, not all the combinations of features described in the embodiments are essential for the solving means of the invention.

  FIG. 1 shows a configuration of a transmission circuit 100 according to the present embodiment. The transmission circuit 100 transmits a signal between the input terminal 110 and the output terminal 120. The transmission circuit 100 transmits a wideband signal including a signal of several tens GHz from a DC signal. The transmission circuit 100 includes an input terminal 110, an output terminal 120, a first high-frequency signal passing unit 130, an input-side low-frequency signal passing unit 140, an output-side low-frequency signal passing unit 145, and a switch unit 150. .

  The input terminal 110 inputs a broadband signal including a DC signal. The output terminal 120 outputs a wideband signal including a DC signal or a high-frequency signal having a predetermined frequency or higher. The input terminal 110 and the output terminal 120 are a low-frequency transmission including a high-frequency transmission path including a first high-frequency signal passing unit 130, an input-side low-frequency signal passing unit 140, a switch unit 150, and an output-side low-frequency signal passing unit 145. It may be a virtual terminal corresponding to a branch point and a junction of the road. Further, the output terminal 120 may be terminated by being connected to the other of the termination resistors that are connected to the reference potential.

  The input terminal 110 and the output terminal 120 may be coaxial connectors according to the signal band to be transmitted. For example, the input terminal 110 and the output terminal 120 are standardized connectors such as an N connector, a BNC connector, an SMA connector, an APC 3.5 connector, a K connector, and an APC 2.4 connector. Instead, the input terminal 110 and the output terminal 120 may be directly fixed to the wiring on the circuit board by soldering or the like without using a connector.

  The first high-frequency signal passing unit 130 blocks a low-frequency signal having a frequency lower than a predetermined reference frequency in the signal from the input terminal 110, and transmits a high-frequency signal having the reference frequency or higher to the output terminal 120. The first high-frequency signal passing unit 130 may be an AC coupling circuit in which capacitive elements are connected in series to the transmission line. Instead, the first high-frequency signal passing unit 130 may be a high-pass filter circuit. The reference frequency of the first high-frequency signal passing unit 130 is determined by elements constituting the circuit.

  The input-side low-frequency signal passing unit 140 passes the low-frequency signal in the signal from the input terminal 110 and attenuates the high-frequency signal. The input-side low-frequency signal passing unit 140 may be an isolator circuit having at least one inductance element provided in series with the transmission line. Here, the material of the inductance element may be ferrite. Instead, the input-side low-frequency signal passing unit 140 may be a resistance element provided in series with the transmission line. Since the input-side low-frequency signal passing unit 140 attenuates the high-frequency signal, the component reflected toward the input terminal 110 can be attenuated even when the high-frequency signal is input.

  The output-side low-frequency signal passing unit 145 passes the low-frequency signal that has passed through the input-side low-frequency signal passing unit 140, transmits the low-frequency signal to the output terminal 120, and attenuates the high-frequency signal from the first high-frequency signal passing unit 130. Let The output side low frequency signal passing unit 145 may be an isolator circuit similar to the input side low frequency signal passing unit 140. Since the output-side low-frequency signal passing unit 145 attenuates the high-frequency signal, the reflected signal from the circuit connected to the output terminal 120 is also attenuated. The output-side low-frequency signal passing unit 145 may be a resistance element that terminates a high-frequency signal.

  The switch unit 150 switches whether to connect between the input-side low-frequency signal passing unit 140 and the output-side low-frequency signal passing unit 145. The switch unit 150 may be a switch such as an FET switch, a relay switch, a photocoupler, an optical MOS switch, or a MEMS switch. Instead, the switch unit 150 may perform switching by selecting whether to amplify using an amplifier.

  The switch unit 150 turns on the connection when the transmission circuit 100 passes a low-frequency signal, and turns off the connection when the transmission circuit 100 does not pass the low-frequency signal to switch the transmission band of the transmission circuit 100. Since the switch unit 150 is a switch for switching the passage of a low-frequency signal, it is not necessary to transmit a high-frequency signal, and a switch with a transmission band matched to the low-frequency signal may be used.

  The transmission circuit 100 according to this embodiment transmits a high-frequency signal having a reference frequency or higher determined by the circuit element of the first high-frequency signal passing unit 130 in the signal input from the input terminal 110 to the output terminal 120. The transmission circuit 100 turns off the switch unit 150 in the case of AC coupling that does not transmit a low-frequency signal lower than the reference frequency including a DC signal. Here, the transmission circuit 100 attenuates the high-frequency signal by the input-side low-frequency signal passing unit 140 and the output-side low-frequency signal passing unit 145 so that the high-frequency signal is not transmitted to the transmission path for transmitting the low-frequency signal. It is possible to transmit a high-frequency signal without any influence.

  When the transmission circuit 100 uses DC coupling for transmitting a low-frequency signal lower than the reference frequency including a DC signal, the transmission unit 100 turns on the switch unit 150. Here, the transmission circuit 100 attenuates the high-frequency signal by the input-side low-frequency signal passing unit 140 and the output-side low-frequency signal passing unit 145 so that the high-frequency signal is not transmitted to the switch unit 150. It is not necessary to consider reflection on the signal. That is, the transmission circuit 100 can switch the transmission of the low frequency signal without the influence of reflection or the like by using an inexpensive switch that switches the transmission of the low frequency signal lower than the reference frequency as the switch unit 150.

  FIG. 2 shows the configuration of the differential signal transmission circuit 200 according to this embodiment together with the differential signal source 210. In the differential signal transmission circuit 200 according to the present embodiment, components that are substantially the same as those of the transmission circuit 100 according to the present embodiment shown in FIG. The differential signal transmission circuit 200 transmits a differential signal between the input terminal 110 and the output terminal 120. The differential signal source 210 is an example of a device that generates a signal having two polarities whose phases are inverted by two transmission lines, and may be a circuit or a device that generates a differential signal.

  The differential signal transmission circuit 200 includes a transmission circuit 100 according to the present embodiment that transmits a first polarity signal that is one of the positive side and the negative side of the differential signal, and the other of the positive side and the negative side of the differential signal. And a transmission circuit 100 according to the present embodiment that transmits a second polarity signal. The differential signal transmission circuit 200 transmits, to the output terminal 120, high-frequency signals that are equal to or higher than the reference frequency in the differential signals respectively input from the input terminal 110.

  The differential signal transmission circuit 200 turns off the two switch units 150 when AC coupling is performed that does not transmit a low frequency signal lower than the reference frequency including a DC signal. Since the differential signal transmission circuit 200 transmits the differential signal using the two transmission circuits 100 according to the present embodiment, the differential signal can be transmitted without being affected by reflection or the like.

  The differential signal transmission circuit 200 turns on the two switch units 150 when DC coupling is used to transmit a low-frequency signal lower than the reference frequency including a DC signal. Here, the differential signal transmission circuit 200 attenuates the high-frequency signal by the input-side low-frequency signal passing unit 140 and the output-side low-frequency signal passing unit 145 so that the high-frequency signal is not transmitted to the switch unit 150. Does not have to take into account reflection of high-frequency signals. That is, the differential signal transmission circuit 200 can switch transmission of a low-frequency differential signal without being affected by reflection or the like, using an inexpensive switch that switches transmission of a low-frequency signal lower than the reference frequency as the switch unit 150. .

  FIG. 3 shows an example of a signal transmission result by the differential signal transmission circuit 200 according to the present embodiment. In the upper side of the figure, the differential signal transmission circuit 200 turns on the two switch units 150 and transmits the low frequency and high frequency of the input differential signal. The waveforms of two rectangular pulses whose phases are reversed are observed, and it can be seen from the waveforms indicated by the solid line and the broken line that the differential signal transmission circuit 200 transmits a differential signal having a common voltage of 600 mV or more.

  In the lower side of the figure, the differential signal transmission circuit 200 turns off the two switch sections 150 and transmits the high frequency of the input differential signal. A differential waveform corresponding to the rising and falling edges of the rectangular pulse is observed centering on 0 V, and the differential signal transmission circuit 200 transmits the high-frequency component of the differential signal from the waveform indicated by the solid line and the broken line. Recognize.

  FIG. 4 shows an example of a signal transmission result by the differential signal transmission circuit 200 according to the present embodiment. FIG. 4 shows the details of the rising and falling waveforms of the pulse by enlarging the time axis compared to FIG. On the upper side of the figure, the differential signal transmission circuit 200 turns on the two switch units 150 and transmits the low frequency and high frequency of the input differential signal. The waveforms of two pulses whose phases are inverted are observed, and it can be seen from the waveforms indicated by the solid line and the broken line that the differential signal transmission circuit 200 transmits a differential signal having a common voltage of 600 mV or more.

  In the lower side of the figure, the differential signal transmission circuit 200 turns off the two switch sections 150 and transmits the high frequency of the input differential signal. A differential waveform corresponding to the rise and fall of the pulse is observed, and it can be seen from the waveforms indicated by the solid and broken lines that the differential signal transmission circuit 200 has transmitted the high-frequency component of the differential signal. From the above observation results, it can be seen that the differential signal transmission circuit 200 can switch the transmission of the low-frequency signal without affecting the transmission of the high-frequency signal.

  FIG. 5 shows a first modification of the differential signal transmission circuit 200 according to the present embodiment. In this modification, the same reference numerals are given to substantially the same operations as those of the differential signal transmission circuit 200 according to the present embodiment shown in FIG. 2, and the description thereof is omitted. The differential signal transmission circuit 200 further includes a termination network unit 510.

  The termination network unit 510 terminates a transmission path for transmitting a low-frequency signal and a transmission path for transmitting a high-frequency signal, respectively. The output-side low-frequency signal passing unit 145 may be a termination resistor that terminates a transmission line that transmits a high-frequency signal. In addition, the termination network unit 510 may provide a second high-frequency signal passing unit 514 between each transmission path of the low-frequency signal and the reference voltage. The termination network unit 510 may include a resistance element 512 that connects between two transmission paths through which a low-frequency signal is transmitted. For example, the second high-frequency signal passing unit 514 may be a capacitive element. Here, the reference voltage may be a ground potential.

  Here, the second high-frequency signal passing unit 514 is a low-impedance element for high-frequency signals and a high-impedance element for DC and low-frequency signals. The termination network unit 510 uses the output-side low-frequency signal passing unit 145 connected to the output terminal 120 as a termination resistor for a transmission path that transmits a high-frequency signal. The second high-frequency signal passing unit 514 passes the terminal current of the high-frequency signal to the ground potential, while preventing transmission of DC and low-frequency signals.

  When the two switch units 150 are turned on, the DC and low-frequency signal components respectively input from the input terminal 110 pass through the output-side low-frequency signal which is a terminal resistor of the high-frequency signal on the side not connected to the output terminal 120. Is supplied to the unit 145 and transmitted to the output terminal 120. Therefore, the differential signal transmission circuit 200 transmits the DC, low frequency signal, and high frequency component to the output terminal 120. Further, the differential signal transmission circuit 200 transmits only the high-frequency component to the output terminal 120 when the two switch units 150 are turned off.

  The two resistance elements 512 may individually terminate DC and low-frequency signals that are transmitted through two low-frequency signal transmission paths. Instead, the connection portions of the two resistance elements 512 may be connected to the reference potential. Although this modification has been described as a circuit for transmitting a differential signal, instead of this, it may be a single-ended transmission line in which a high-frequency and low-frequency transmission line from the input terminal 110 to the output terminal 120 is a set. .

  FIG. 6 shows a second modification of the differential signal transmission circuit 200 according to the present embodiment. In this modification, the same reference numerals are given to substantially the same operations as those of the differential signal transmission circuit 200 according to the present embodiment shown in FIG. 2, and the description thereof is omitted. The differential signal transmission circuit 200 further includes an amplifying unit 610 and a reference voltage changing unit 620.

  The amplifying unit 610 is provided in each of the first and second transmission circuits, and amplifies and outputs the signal from the input-side low frequency signal passing unit 140. The amplification unit 610 may include a differential amplification circuit 612 and a reference voltage unit 614. The differential amplifier circuit 612 outputs a difference between the two signals output from the input-side low-frequency signal passing unit 140 in the first and second transmission circuits. The reference voltage unit 614 outputs a preset voltage. The reference voltage unit 614 may output a voltage that should be the common voltage of the differential signal, and may output the threshold voltage of the amplification unit 610 instead. One reference voltage unit 614 may be connected to each of the two differential amplifier circuits 612 in the first and second transmission circuits.

  The reference voltage changing unit 620 varies the output voltage of the reference voltage unit 614. The reference voltage changing unit 620 may output different output voltages to the reference voltage unit 614 in the first and second transmission circuits. The amplifying unit 610 outputs a signal corresponding to a preset reference voltage and an input signal. Instead, for example, the reference voltage changing unit 620 modulates the reference voltage unit 614 with a constant modulation signal.

  The amplifying unit 610 can amplify the low frequency signal according to the reference signal and the input signal in the low frequency signal transmission path in which the high frequency signal is attenuated. When the two switch sections 150 are turned on, the differential signal transmission circuit 200 can superimpose the offset voltage on the signal input from the input terminal 110 and output the signal from the output terminal 120. When the two switch units 150 are turned off, the differential signal transmission circuit 200 can transmit only a high-frequency signal.

  Here, the differential signal transmission circuit 200 may omit the switch unit 150 by replacing the switching of the switch unit 150 with the switching of the amplification degree of the amplification unit 610 or the like. Further, the differential signal transmission circuit 200 may omit the switch unit 150 when it is known that the switch unit 150 is always used in the ON state. Although this modification has been described as a circuit for transmitting a differential signal, it may be replaced with a single-ended transmission line with a single transmission line.

  FIG. 7 shows a third modification of the differential signal transmission circuit 200 according to the present embodiment. In this modification, the same reference numerals are given to the substantially same operations as those of the second modification of the differential signal transmission circuit 200 according to the present embodiment shown in FIG. 6, and the description thereof is omitted. The differential signal transmission circuit 200 shows an example in which the position where the switch unit 150 in FIG. 6 is provided is changed from the subsequent stage to the previous stage.

  Thus, the differential signal transmission circuit 200 can completely turn off the input signal of the amplifying unit 610 when the low-frequency transmission is turned off. Further, by making the output side low frequency signal passing unit 145 a circuit including a series connection of a resistance element and an inductance element, the amplifying unit 610 and the output side low frequency signal passing unit 145 can be a bias T circuit.

  FIG. 8 shows a fourth modification of the differential signal transmission circuit 200 according to the present embodiment. In this modification, the same reference numerals are given to substantially the same operations as those of the first or third modification of the differential signal transmission circuit 200 according to the present embodiment shown in FIG. To do. The differential signal transmission circuit 200 further includes a second high-frequency signal passing unit 514.

  The output-side low-frequency signal passing unit 145 may be a termination resistor that terminates a transmission line that transmits a high-frequency signal. The second high-frequency signal passage unit 514 is provided between at least one low-frequency signal transmission path and the reference voltage. The second high-frequency signal passing unit 514 may be a capacitive element. Here, the reference potential may be a ground potential. The second high-frequency signal passing unit 514 is a low-impedance element for high-frequency signals and a high-impedance element for DC and low-frequency signals. In addition, the differential signal transmission circuit 200 may be a terminating resistor of a transmission path for transmitting a high-frequency signal through the output-side low-frequency signal passing unit 145. As a result, the differential signal transmission circuit 200 turns on the switch unit 150 to superimpose the amplified signal of the difference between the low-frequency signals input to the two input terminals 110 on the high-frequency signal and output it from the output terminal 120. Can do. Although this modification has been described as a circuit for transmitting a differential signal, instead of this, it may be a single-ended transmission line in which a high-frequency and low-frequency transmission line from the input terminal 110 to the output terminal 120 is a set. .

  FIG. 9 shows a fifth modification of the differential signal transmission circuit 200 according to the present embodiment. In this modification, the same reference numerals are given to the substantially same operations as those of the fourth modification of the differential signal transmission circuit 200 according to the present embodiment shown in FIG. 8, and the description thereof is omitted. The differential signal transmission circuit 200 further includes a resistance element 910 and a reference voltage unit 920 in each of the two transmission paths.

  One resistance element 910 is provided between the output of the input-side low-frequency signal passing unit 140 of the first transmission path and one reference voltage unit 920. The amplification unit 610 of the first transmission line uses the output of the input-side low-frequency signal passing unit 140 of the first transmission line and the reference voltage of the reference voltage unit 920 as input signals.

  Similarly, the second transmission line is provided with another resistance element 910 between the output of the input-side low-frequency signal passing unit 140 of the second transmission line and the other reference voltage unit 920. The amplification unit 610 of the second transmission path uses the output of the input-side low-frequency signal passing section 140 and the reference voltage unit 920 of the second transmission path as input signals. As a result, the differential signal transmission circuit 200 can individually adjust the offset voltages of the two transmission paths. The reference voltage unit 920, the resistance element 910, and the input-side low-frequency signal passing unit 140 may have a function of a bias T with respect to the input terminal 110 that supplies the DC and low-frequency signal that drives the amplification unit 610. . Although this modification has been described as a circuit for transmitting a differential signal, instead of this, it may be a single-ended transmission line in which a high-frequency and low-frequency transmission line from the input terminal 110 to the output terminal 120 is a set. .

  FIG. 10 shows a configuration example of the test apparatus 1000 according to the present embodiment, together with the device under test 10. The test apparatus 1000 tests at least one device under test 10 such as an analog circuit, a digital circuit, an analog / digital mixed circuit, a memory, and a system on chip (SOC). The test apparatus 1000 inputs a test signal based on a test pattern for testing the device under test 10 to the device under test 10, and the device under test based on an output signal output from the device under test 10 according to the test signal. 10 pass / fail is determined.

  The test apparatus 1000 includes a test signal generation unit 1010, a signal input / output unit 1020, and an expected value comparison unit 1030. The test signal generator 1010 generates a plurality of test signals to be supplied to the device under test 10. The test signal generator 1010 may generate an expected value of the response signal output from the device under test 10 according to the test signal. The test signal generator 1010 may be connected to the plurality of devices under test 10 via the signal input / output unit 1020 to test the plurality of devices under test 10.

  The signal input / output unit 1020 is connected to one or more devices under test 10 and exchanges test signals between the test apparatus 1000 and the devices under test 10. The signal input / output unit 1020 may be a performance board on which a plurality of devices under test 10 are mounted.

  The expected value comparison unit 1030 compares the received data value received by the signal input / output unit 1020 with the expected value. The expected value comparison unit 1030 may receive the expected value from the test signal generation unit 1010. The test apparatus 1000 may determine pass / fail of the device under test 10 based on the comparison result of the expected value comparison unit 1030.

  The test apparatus 1000 may use single-ended signal transmission for transmission of signals exchanged between the signal input / output unit 1020 and the device under test 10. The test apparatus 1000 may execute single-end signal transmission by the transmission circuit 100 according to the present embodiment. As a result, the test apparatus 1000 can switch between DC coupling and AC coupling for single-ended signal transmission. In addition, the test apparatus 1000 can switch and transmit the offset voltage superposition.

  Instead of this, the test apparatus 1000 may use differential signal transmission for transmission of signals exchanged between the signal input / output unit 1020 and the device under test 10. Then, the test apparatus 1000 may execute differential signal transmission by the differential signal transmission circuit 200 according to the present embodiment. Accordingly, the test apparatus 1000 can switch between DC coupling and AC coupling for differential signal transmission. In addition, the test apparatus 1000 can switch and transmit the offset voltage superposition.

  As mentioned above, although this invention was demonstrated using embodiment, the technical scope of this invention is not limited to the range as described in the said embodiment. It will be apparent to those skilled in the art that various modifications or improvements can be added to the above-described embodiment. It is apparent from the scope of the claims that the embodiments added with such changes or improvements can be included in the technical scope of the present invention.

  The order of execution of each process such as operations, procedures, steps, and stages in the apparatus, system, program, and method shown in the claims, the description, and the drawings is particularly “before” or “prior to”. It should be noted that the output can be realized in any order unless the output of the previous process is used in the subsequent process. Regarding the operation flow in the claims, the description, and the drawings, even if it is described using “first”, “next”, etc. for convenience, it means that it is essential to carry out in this order. It is not a thing.

DESCRIPTION OF SYMBOLS 10 Device under test 100 Transmission circuit 110 Input terminal 120 Output terminal 130 1st high frequency signal passage part 140 Input side low frequency signal passage part 145 Output side low frequency signal passage part 150 Switch part 200 Differential signal transmission circuit 210 Differential signal Source 510 Termination network unit 512 Resistive element 514 Second high-frequency signal passing unit 610 Amplifying unit 612 Differential amplifier circuit 614 Reference voltage unit 620 Reference voltage changing unit 910 Resistance element 920 Reference voltage unit 1000 Test device 1010 Test signal generating unit 1020 Signal Input / output unit 1030 Expected value comparison unit

Claims (21)

A transmission circuit for transmitting a signal between an input terminal and an output terminal,
A first high-frequency signal passing unit that cuts off a low-frequency signal lower than a predetermined reference frequency in a signal from the input terminal and transmits a high-frequency signal that is equal to or higher than the reference frequency to the output terminal;
An input-side low-frequency signal passing unit that passes the low-frequency signal in the signal from the input terminal and attenuates or insulates the high-frequency signal;
An output-side low-frequency signal that passes through the low-frequency signal that has passed through the input-side low-frequency signal passing unit and transmits the low-frequency signal to the output terminal and attenuates or insulates the high-frequency signal from the first high-frequency signal passing unit. A passing section;
A switch unit for switching whether to connect between the input side low frequency signal passing unit and the output side low frequency signal passing unit;
A transmission circuit comprising:   The apparatus according to claim 1, further comprising: an amplifying unit that is connected between the input-side low-frequency signal passing unit and the output-side low-frequency signal passing unit and that amplifies and outputs a signal from the input-side low-frequency signal passing unit. Transmission circuit.   The output-side low-frequency signal passing section has a second high-frequency signal passing through which one end is connected to a transmission path for transmitting the low-frequency signal and the other end is connected to a reference voltage to pass a high-frequency signal to the reference voltage side. The transmission circuit according to claim 2, further comprising a portion.   The transmission circuit according to claim 2, wherein the amplification unit outputs a signal corresponding to a preset reference voltage and an input signal.   The transmission circuit according to claim 4, further comprising a reference voltage changing unit that varies the voltage of the reference voltage.   The transmission circuit according to claim 5, wherein the reference voltage changing unit changes the reference voltage with time.   The transmission circuit according to claim 1, further comprising a termination network unit that includes the output-side low-frequency signal passing unit and terminates the high-frequency signal and the low-frequency signal.   The output-side low-frequency signal passing section has a second high-frequency signal passing through which one end is connected to a transmission path for transmitting the low-frequency signal and the other end is connected to a reference voltage to pass a high-frequency signal to the reference voltage side. The transmission circuit according to claim 1, further comprising a portion.   2. The transmission circuit according to claim 1, wherein at least one of the input-side low-frequency signal passing unit and the output-side low-frequency signal passing unit includes at least one inductance element provided in series with a transmission path. A differential signal transmission circuit for transmitting a differential signal between an input terminal and an output terminal,
The first transmission circuit according to claim 1, which transmits a signal having a first polarity of the differential signal;
The second transmission circuit according to claim 1, wherein the second transmission circuit transmits a second polarity signal of the differential signal.
A differential signal transmission circuit comprising:   The differential signal transmission circuit according to claim 10, further comprising a termination network unit that includes the output-side low-frequency signal passing unit and terminates the high-frequency signal and the low-frequency signal of the differential signal.   Each of the said 1st and 2nd transmission circuit is a differential signal transmission circuit of Claim 10 provided with the amplification part which amplifies and outputs the signal from the said input side low frequency signal passage part.   The amplifying unit of the first and second transmission circuits includes a differential amplifying circuit that outputs a difference between two signals output by the input-side low-frequency signal passing unit in the first and second transmission circuits. The differential signal transmission circuit according to claim 12, each including a differential signal transmission circuit.   The differential signal transmission circuit according to claim 12, wherein the amplifying units of the first and second transmission circuits respectively output a signal corresponding to a preset reference voltage and an input signal.   The differential signal transmission circuit according to claim 14, further comprising a reference voltage changing unit that varies the voltage of the reference voltage.   The differential signal transmission circuit according to claim 15, wherein the reference voltage changing unit changes the reference voltage with time.   At least one of the first and second transmission circuits has a second end that is connected to a transmission path that transmits the low-frequency signal and the other end that is connected to a reference voltage. The second transmission circuit passes the high-frequency signal to the reference voltage side. The differential signal transmission circuit according to claim 10, further comprising: a high-frequency signal passing portion.   At least one of the first and second transmission circuits has a second end that is connected to a transmission path that transmits the low-frequency signal and the other end that is connected to a reference voltage. The second transmission circuit passes the high-frequency signal to the reference voltage side. The differential signal transmission circuit according to claim 12, further comprising: a high-frequency signal passing portion.   At least one of the input-side low-frequency signal passing unit and the output-side low-frequency signal passing unit in the first and second transmission circuits includes at least one inductance element provided in series in the transmission path. The differential signal transmission circuit according to claim 10.   The differential signal transmission circuit according to claim 19, wherein a material of the inductance element is ferrite. A test apparatus for testing a device under test,
A test signal generator for generating a plurality of test signals to be supplied to the device under test;
A signal input / output unit for inputting / outputting a signal to / from the device under test;
With
A test apparatus for transmitting a signal between the signal input / output unit and the device under test using the transmission circuit according to claim 1.

Images